Devices that produce magnetic fields can have broad applications in biotechnology and medicine. For example, magnetic fields generated by such devices have applications in cancer diagnostics, drug discovery, and stem cell research, among others. One particular area includes magnetic separation of cells, in which cells of interest are attached to magnetic biomarkers in a solution and the solution is then introduced into an area having a magnetic field. The magnetic field serves to isolate and/or filter the cells having the attached biomarkers for subsequent analysis, modification, or use.